Forming some 20 Vartarg brass just a couple of observations

[Mr Underbridge]

Just some maybe useful or interesting observations.
I was using Lapua 221 fireball brass. Turned it as 221 fireball brass first, it started as 0.0138 neck thickness, I turned it to my desired thickness of 0.0125.

Now when I cut 221 fireball to 0.0125 neck thickness my neck thickenss was very consistent within 0.0001 inches at most as i took measurments at several spots on the neck, I use a certified mitotuyo gauge to check my micrometer and the force i use to measure.

I finally ran it through a 20 Vartarg FL redding bushing die two times using a smaller bushing each step. My neck thickness grew to average of 0.0137 inches.
When I measured the neck wall thickness on my cases after running them through the bushing the thickness varied 0.0005 or so inches on the same piece of brass and I took a bunch of sample same thing.
Wondering what could cause that?
Any way, today I will run the brass through 20 caliber expander and trim it one last time to my desired thickness and hopefully it should solve this inconsistency problem. I will let you know this friday.

 

[dgeesaman]

It makes sense that the metal gets thicker as the diameter gets smaller. A little bit goes into adder neck length but most goes into becoming thicker.

I would run an expander through it (or a couple samples) to eliminate any waviness or taper from the necking down and guarantee you have an accurate neck thickness measurement. Then skim to final thickness.

 

[Gabe22BR]

turn it after you neck it down to 20cal will help, best if it has been shot once....